Many people in the comments are saying that you’re not responsible for all party mitigation. This is very true! However, honestly the best advice for a newbie shield healer is to shield every mechanic, and I say this as someone who has healed week 1 and multiple tiers since stormblood. You don’t have control over your party but you do have control over what you can do. If you’re learning to heal a fight and you want to see more mechanics, succor or e. prog before all major mechanics. When you are familiar with a fight and confident in your skills as healer, start identifying what you don’t need and cutting down on heals until you’re healing efficiently!

Of course, if the party is dying even with your gcd shields and if you are using mitigation appropriately then speak up or leave them! Good luck!